Rubber covered roller



Oct. 10, 1967 R. R. MELTZ RUBBER COVERED ROLLER Filed June 14, 1966 l/VVf/VTOR.

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United States Patent M 3,345,942 1 RUBBER COVERED ROLLER Robert R. Meltz, Philadelphia, Pa., assignor to The Moreland Corporation, Willow Grove, Pa., a corporation of Pennsylvania Filed June 14, 1966, Ser. No. 564,710 9 Claims. (Cl. 101348) ABSTRACT OF THE DISCLOSURE A roller having a covering comprising rubber having polytetrafluoroethylene particles uniformly dispersed therein. The roller is particularly adapted for use as a form roller in an inking system.

This invention relates to rollers, and more particularly, to rubber covered rollers.

In certain processes, it is necessary that release properties be present in the rubber covering of rollers. It has been customary to use a heat-shrinkable tube of polytetrafluoroethylene for obtaining these properties. The tube is shrunk to the contours of the rubber covering 0n the roller by applying heat, and presents a surface that is resistant to corrosive agents, is insoluble, non-adhesive, non-flammable, and has a low coefficient of friction. It is necessary to etch the inside of the tube with such maerials as sodium salts to produce an area that can be bonded to the substrate which could be steel, wood, rubber or plastic. Various adhesive systems, such as epoxy resins, are used to accomplish the bond. With this method of covering a roller, the Shore A hardness of the surface, regardless of the softness of the substrate will measure between 55 and 65. It is necessary to limit the operating pressures to low perlineal-inch-face values to prevent the sleeve from breaking loose during service.

The rubber covered roller of this invention eliminates the need for the separate tube covering. Thus, the rubber covering embodying the composition of this invention enjoys all of the properties that are obtainable with the polytetrafiuoroethylene tube, and in addition, possesses a number of further advantages of its own which cannot be obtained through using the polytetrafluoroethylene tube.

The roller of this invention can be used wherever rubber covered rollers have been used in the past. Thus it can be used for the rolling of steel, the conveying of steel, the application of sizing to textiles and in the printing industry for the rolling of ink onto printing plates. A specific advantageous use of the roller of this invention is as a form roller in an inking system for printing. When used as a form roller, the hicky roller generally used in the inking system can 'be eliminated. Thus, the

roller of this invention serves the dual function of being a form roller and a hickey roller.

Hickies are described on pages 12.50 to 12.53 of The Lithographics Manual, 20th Anniversary Edition, Volume Two, published January 1958 by Waltwin Publishing Company, New York. As described in said manual, when running a lithographic offset press it is important to make certain that no hickies or spots appear on the print. Hickies are described as appearing, under magnification, as having a circular cross-section with a raised center. Once hickies appear, they repeat on sheet after sheet in the same places and increase in number as the run progresses. They are caused by solid, more or less ink-receptive particles that are stuck to the blanket or plate, and which are not transferred to the paper or dislodged by the form rollers. It takes a wash-up or a hickey roller to get rid of them, but, unless their source is removed they start coming back as soon as the run is resumed.

White or light spots in the work can, like hickies, be caused by particles or fibers stuck to the blanket or plate. The only difference is that instead of being inkreceptive, these particles are water-receptive. The main source of particles that cause hickies and spots are ink and paper. But a dirty press, a dirty ceiling or poor rollers can also supply particles of foreign matter.

More hickies are probably caused by ink skin, that is, dried ink, than by anything else. These hickies can usually be recognized by their shape and appearance. Once they are identified the only thing to do is Wash up the press, discard'the ink and load the fountain with a fresh skin-free batch of ink.

Paper is second to ink as a source of hickies. It can produce hickies as well as several kinds of spots. Paper dust, resulting from the slitting and cutting of paper at the middle, is one source. Small areas of surface fibers or coating are sometimes picked, stick to the blanket or plate and produce hickies or spots that repeat sheet after sheet. Slitting and sheeting of paper sometimes sets free individual fibers that get trapped between the sheets. Fibers, loosely bonded'in the paper surface are pulled out of the sheet by the ink, quickly become saturated with water, refuse to take fresh ink and leave white images of themselves in the printed work.

Hickies can also be caused by particles of dust or dirt falling from a dirty ceiling, or dislodge from a dirty press or from disintegrating rollers.

It is now a common practice to add a special hickey roller to all inking systems in order to prevent hickies or spots. The hickey roller is a leather covered roller, a cast urethane covered roller or a rubber covered roller, where the rubber covering contains a tackifying agent that bleeds slowly to the surface of the rubber cover and presents a sticky surface that collects and holds the hickies.

The rubber covered roller of this invention will completely eliminate the need for a hicky roller. The exact mechanism by which the roller carries out this function is not known, but it is believed that the composition of the rubber covering develops a static charge which attracts the hickies and holds them in place. The rubber covered roller of this invention also serves the function of a form roller. Therefore, the roller of this invention can be used in place of a normal form roller and completely eliminate the need for an additional hicky roller.

It is therefore an object of this invention to provide a novel rubber covered roller.

It is another object of this invention .to provide a rubber covered roller which gives release properties at operating temperatures of 0 to 600 F.

It is a further object of this invention to provide a roller that can be ground after surface damage to the covering and still provide release properties.

It is a further object of this invention to provide a roller that hasthe Shore A hardness of the rubber covering, whether it be 1 or plus.

It is a further object of this invention to provide a rubber covered roller that will give release properties,

It is a further object of this invention to provide a rubber covered roller which has improved chemical resistance.

These and other objects of this invention are accomplished by providing a roller comprising a roller body and a covering bonded to said body, said covering compris ing rubber having polytetrafluoroethylene particles uniformly dispersed therein.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a front elevational view of a roller embodying the present invention;

FIG. 2 is an enlarged sectional view taken in the area 2 of FIG. 1; and

FIG. 3 is an inking system including rollers embodying the present invention.

Referring now in greater detail to the various figures of the drawings wherein similar reference characters refer to similar parts, a rubber covered roller embodying the present invention is general-1y shown at 10 in FIG. 1. Roller 10 includes the usual metal roll body 12 with a rubber covering 14. Uniformly dispersed throughout the rubber covering 14 are Polytetrafluoroethylene particles 16.

The use of the roller of this invention in an inking system is shown in FIG. 3. The inking system includes an ink fountain 18, a doctor blade and trough 20, and an adjustment screw 22. Any of the conventional rollers used in an inking system can be used in the inking system embodying the roller of this invention. Thus the system can include a fountain roller 24, a doctor roller 26, a vibrator 28, an intermediate roller 30, and a center vibrator roller 32. Distributor roller 34 contacts vibrator roller 32 and has a rider 36 thereon. Intermediate rollers 38 transfer the ink to drums 40. Drums 40 in turn contact form rollers 42, 44, 46 and 48. The form rollers in turn will transfer ink to the plate cylinder 50.

The roller of this invention will be the last form roller to apply ink to the blanket or plate. Thus, if the plate cylinder is rotating in the direction of arrow 52 roller 48 would be a roller embodying the present invention. If two rollers embodying the present invention are to be used then roller 42 would also constitute one of the rollers of this invention.

The roller of this invention comprises a conventional roller body having a rubber covering with olytetrafluoroethylene particles dispersed uniformly through the covering. As used herein, rubber refers to natural rubber, synthetic rubbers, and mixtures thereof. The polytetrafluoroethylene particles range in size from 0.5 micron to particles having a fineness of 99.5 percent through a 325 mesh screen, which is approximately 44 microns. The preferred particle size for the polytetrafluoroethylene is to microns. The polytetrafluoroethylene will be present in a range of 0.5 to 200 parts by weight for every hundred parts by weight of rubber. Any of the normal rubber additives, such as curing agents, pigments, fillers, and plasticizers can be present in the compositions.

Specific compositions embodying the rubberolytetrafluoroethylene mixtures of this invention can be found in the following examples. In these examples the function of each of the ingredients follows the name of the ingredient:

Example 1 Parts by weight Acrylonitrile butadiene copolymer-synthetic rubber base 100.00

4 Dioctyl phthalateplasticizer 15.00 Sodium silico al-uminate-filler 75.00 Benzothiazole disulfide-accelerator and/or vulcanizing agent -i 1.25 Stearic acidactivator .50 Polytetrafluoroethylene particles 40.00

Example 2 Parts by weight Polymer of 2-chlorobutadiene 1,3-synthetic rubber base 100.00

Example 3 Parts by weight #1 ribbed smoked sheets-natural rubber base 100.00

Extra light calcined magnesia-acid acceptor 5.00 N-phenyl-beta-naphthylamine-antioxidant 2.00 Zinc oxide-activator 5.00 Light process oil 10.00 Stearic acidactivator and processing aid 3.00 Semi-reinforcing furnace blackfiller 25.00 Hard rubber dustfiller-processing aid 75.00 Sulfurcuring agent 35.0 0 Polytetrafluoroethylene particles 200.00

Other rubbers which may be used are acrylic ester/acrylonitrile copolymers, styrene-butadiene rubber, chlorosulfonated polyethylene, fluoroelastomers, isobutyleneisoprene copolymers, stereo polybutadienes, stereo polyisoprenes, organic polysulfide rubber, polyether and polyester urethane polymers, and ethylene-propylene terpolymers.

The polytetrafluoroethylene additive can also be used in such polymers as polypropylene oxides, polyepichlorohydrins, and copolymers of epichlorohydrin and ethylene oxide, silicones, and blends of the various polymers specified above.

The compositions used in covering the rolls are formulated by first breaking down the rubber to a uniform plastic mass on a mill or in an internal mixer, such as a Banbury mixer. Thereafter the olytetrafluoroethylene powder particles are added and the mixing is continued. The remaining compounding ingredients, except for the curing agents, are then added to the blend. The compound is aged and is then placed on a two roll rubber mill,

broken down or warmed up until a smooth, uniform band forms around one roll, and the curing agents are added and thoroughly blended.

After all the curing agents have been thoroughly blended into the composition, the stock is then strained and c-alendered into a sheet form or extruded as a tube. The tube can be extruded directly onto the primed and cemented metal roll body, or can be slipped onto the body subsequent to the extrusion. The calendered sheet is wrapped around the primed and cemented body, using a roll-building machine. The rollers are then blocked, wrapped with tape under tension, and the rubber is vulcanized or cured by placing the rolls in autoclaves or vulcanizers, where steam and air are present under pressure.

The rubber covered rolls can then be subjected to any of the normal grinding and finishing processes. Thereafter the roller is ready for use and can be used in any of the processes normally associated with rubber covered rollers. As the roller is worn down in use, the polytetrafluoroethylene particles will continue to appear at the surface of the roller since they are uniformly dispersed throughout the rubber composition of the covering. Thus, the surface of the rubber covered roller of this invention will continually be smooth to the touch and will feel like a polytetrafluoroethylene film is on the surface of the rubber. Furthermore, if the covering should be damaged in use, the surface can be reground and still provide the same smooth outer surface and the desired release properties.

As pointed out above, one of the prime uses of the rubber covered roller of this invention is as a form roller in an inking system such as that shown in FIG. 3. When so used as a form roller, it has been found that in addition to supplying ink to the printing cylinder 50, the roller will also attract any dirt particles or paper fibers to its surface and maintain them on its surface. In this way, the roller serves the dual function of being a form roller and a hicky roller, and obviates the necessity of having a separate hicky roller. The form rollers embodying the present invention can periodically be cleaned in order to remove any of the dirt or other particles which could cause hickies or spots. Because of the presence of the polytetrafluoroethylene powder in the surface of the roller, cleaning of the roller is far easier than could be accomplished if the roller comprised rubber without the polytetrafluoroethylene additive.

It has been found that the rollers covered with the composition of this invention can vary in surface hardness according to the composition of the rubber and the amount of polytetrafluoroethylene added. Contrasted with this, the rollers having the bonded polytetrafluoroethylene sleeve always have a surface hardness of 55 to 65 Shore A regardless of the hardness of the surface of the base roller.

Without further elaboration, the foregoing will so fully illustrate my invention, that others may, by applying current or future knowledge, adapt the same for use under various conditions of service.

What is claimed as the invention is:

1. A roller comprising a roller body and a covering bonded to said body, said cover comprising rubber having polytetrafluoroethylene particles uniformly dispersed therein, said polytetrafluoroethylene being present in the range of 0.5 to 200 parts by weight for every parts by weight of rubber.

2. The roller of claim 1 wherein said rubber comprises natural rubber.

3. The roller of claim 1 wherein said rubber comprises synthetic rubber.

4. The roller of claim 1 wherein said polytetrafluoroethylene particles are in a size within the range of 0.5 micron to 44 microns.

5. In an inking system comprising a fountain, ink transferring rollers for transferring ink from said fountain to a plate and at least one form roller for depositing ink on said plate, said form roller being in contact with at least one of said ink transferring rollers, the improvement comprising a covering on said form roller comprising rubber having polytetrafluoroethylene particles uniformly dispersed therein.

6. The inking system of claim 5 wherein said rubber comprises natural rubber.

7. The inking system of claim 5 wherein said rubber comprises synthetic rubber.

8. The inking system of claim 5 wherein said polytetrafiuoroethylene particles are in a size within the range of 0.5 micron to 44 microns.

9. The inking system of claim 5 wherein said polytetrafluoroethylene is present in the range of 0.5 to 200 parts by weight for every hundred parts by Weight of rubber.

References Cited UNITED STATES PATENTS 2,551,060 5/ 1951 Simmons 101232 2,945,773 7/ 1960 Panagrossi et a1. 3,081,206 3/1963 Remer. 3,139,826 7/ 1964 Rainwater 101-348 3,223,676 12/1965 Rucker 260-889 XR FOREIGN PATENTS 650,533 10/ 1962 Canada 260-889 ROBERT E. PULFREY, Primary Examiner. F. A. WINANS, Assistant Examiner. 

5. IN AN INKING SYSTEM COMPRISING A FOUNTAIN, INK TRANSFERRING ROLLERS FOR TRANSFERRING INK FROM SAID FOUNTAIN TO A PLATE AND AT LEAST ONE FORM ROLLER FOR DEPOSITING INK ON SAID PLATE, SAID FORM ROLLER BEING IN CONTACT WITH AT LEAST ONE OF SAID INK TRANSFERRING ROLLERS, THE IMPROVEMENT COM- 